U.S. patent number 4,697,962 [Application Number 06/761,970] was granted by the patent office on 1987-10-06 for control system for a continuous process venturi accelerated pneumatic pump.
This patent grant is currently assigned to Coalair Systems Limited Partnership. Invention is credited to Richard M. Dunbar, Henry E. Stoiber, Charles E. Wynosky.
United States Patent |
4,697,962 |
Dunbar , et al. |
October 6, 1987 |
Control system for a continuous process venturi accelerated
pneumatic pump
Abstract
An apparatus for feeding product to a pipeline via a venturi
assembly has first and second tanks adapted to separately hold a
quantity of product. The product is fed to the tanks from a supply
hopper and enters each tank through an upper opening which
accommodates a feed chute. The open end of each feed chute is
closable by a flapper door which is swingable between open and
closed positions. Pressurized air from a compressor is used to
selectively close the flapper doors via a set of pressure valves
which control the flow of air into the tanks. The product is fed
from each tank to the pipeline through a Y-shaped housing and the
venturi assembly. The housing has respective lower openings for
each tank, also closable by swingable flapper doors. When the upper
doors are closed by the air pressure, the product is forced out of
the tank into the pipeline. A plurality of sensors are provided for
sensing the product level in the tanks and a plurality of detectors
are provided for indicating when the flapper doors are closed. A
controller automatically monitors the sensors and detectors, and
regulates feed of the product into the tanks and the pressure
valves so as to maintain a continuous duty operation in which
product is discharged from one tank as the other tank fills.
Inventors: |
Dunbar; Richard M. (Oakdale,
MN), Wynosky; Charles E. (Minersville, PA), Stoiber;
Henry E. (Lakeland, FL) |
Assignee: |
Coalair Systems Limited
Partnership (New York, NY)
|
Family
ID: |
25063753 |
Appl.
No.: |
06/761,970 |
Filed: |
August 2, 1985 |
Current U.S.
Class: |
406/15; 406/22;
406/27; 406/120; 406/25; 406/32 |
Current CPC
Class: |
B65G
53/12 (20130101); B65G 53/14 (20130101); B65G
53/36 (20130101) |
Current International
Class: |
B65G
53/12 (20060101); B65G 53/04 (20060101); B65G
53/14 (20060101); B65G 057/66 () |
Field of
Search: |
;406/25-27,144,12,120,153,24,32,15,22 ;222/144.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Nase; Jeffrey V.
Attorney, Agent or Firm: Pearne, Gordon, McCoy &
Granger
Claims
What is claimed is:
1. An apparatus for feeding product under steady-state conditions
into a pipeline for pneumatic conveyance by carrier gas flowing
through the pipeline at a predetermined pressure, comprising first
and second upright tanks in combination with a venturi assembly
adapted to introduce product into a pressurized pipeline for
pneumatic conveyance, said tanks being arranged to separately hold
a quantity of the product, each tank having an associated upper
opening for receiving product through a supply means from a supply
thereof and an associated lower opening for feeding product from
the tank into said venturi assembly during a discharge period,
means for selectively opening and closing said upper and lower
openings, said upper openings being normally open and said lower
openings being normally closed, means for selectively pressurizing
each tank to a pressure above the pipeline pressure when said
associated upper opening is closed to cause the product to flow
from the tank into the venturi assembly through said associated
lower opening, means for sensing a predetermined fill level of the
product in each tank, means associated with each tank for detecting
whether said upper and lower openings are closed, and control means
for automatically regulating feed of the product into the venturi
assembly in response to indications received from said sensing and
detecting means to provide controlled continuous duty operation of
said apparatus by verifying proper and alternate product flow into
and out of said tanks wherein one tank is discharging product into
the venturi assembly as the other tank is filling with product,
said control means verifying prior discharge of product from said
other tank to be filled by monitoring said sensing means, if
discharge is not verified, said control means deactivating said
supply means and activating said pressurizing means to temporarily
pressurize said other tank to effect discharge thereof; if
discharge is verified, said control means then activating said
pressurizing means to pressurize said one tank to be discharged
when said sensing means indicates said one tank is filled and said
detecting means indicates said associated lower opening is
closed.
2. An apparatus according to claim 1, wherein said control means
include recycle means and the step of temporarily pressurizing said
other tank is repeated for a predetermined number of times prior to
shutdown of the apparatus.
3. An apparatus according to claim 1, wherein said control means
includes a programmable controller which monitors said sensing and
detecting means and actively controls said pressurizing means based
on a predetermined set of conditions of said monitored means,
including said fill level of product in each tank and closure of
said upper and lower openings.
4. An apparatus according to claim 3 wherein activation of said
pressurizing means closes said associated upper opening of said one
tank and said associated lower opening opens at a predetermined
pressure.
5. An apparatus according to claim 4, wherein said pressurizing
means includes compressor means for providing pressurized air to
said tanks and valve means for individually controlling pressure in
each tank.
6. An apparatus according to claim 5, wherein air under pressure
entering said tanks applies a force on said closing means to close
said associated upper opening.
7. An apparatus according to claim 3, further comprising venting
means in each tank for selectively venting said tanks to ambient
pressure, said venting means being actuated by said control means
and being closed during a discharge period.
8. An apparatus according to claim 7, wherein said control means
opens said venting means after said discharge period in said one
tank and thus prevents said one tank from pressurizing when said
other tank is subsequently being pressurizied, said venting means
in said one tank being operated alternately with said venting means
in said other tank.
9. An apparatus according to claim 8, wherein said control means
includes timer means for determining pressurizing time to discharge
product from each tank.
10. An apparatus according to claim 9, wherein said control means
deactivates said tank pressurizing means when said timer means
times out.
11. An apparatus according to claim 10, wherein said control means
shuts down the apparatus when said associated lower opening is not
closed prior to pressurizing the corresponding tank.
12. An apparatus according to claim 3, wherein said control means
verifies prior discharge in said other tank by monitoring said
sensing means to determine the absence of product in said other
tank.
13. An apparatus according to claim 12, wherein said supply means
for feeding product to said tanks includes supply valve means for
controlling flow of the product from said supply of product to said
tanks, said supply valve means being actuated by said control
means.
14. An apparatus according to claim 13, wherein said supply means
include a common product feed inlet and said supply valve means is
a butterfly valve arranged to control flow of product through said
inlet.
15. An apparatus according to claim 14, wherein said sensing means
is a level probe and said detecting means is a proximity switch
which detects the position of a flapper door which opens and closes
said upper and lower openings.
16. An apparatus according to claim 15, further comprising means
for sensing the pipeline pressure, said control means monitoring
said pressure sensing means and shutting down the apparatus when
the pipeline pressure exceeds predetermined high or low limits.
17. A continuous duty apparatus for feeding product to a pipeline
through a venturi assembly for pneumatic conveyance by primary
carrier gas flowing through the pipeline at a predetermined
pressure, comprising first and second upright tanks in combination
with a venturi assembly adapted to introduce product into a
pressurized pipeline for pneumatic conveyance, said tanks being
arranged to separately hold a quantity of product, each tank having
an associated upper opening for receiving product into the tank
through a supply means from a product supply and having an
associated lower opening for feeding product from the tank into
said venturi assembly during a discharge period, said supply means
including supply valve means for controlling flow of the product
from the product supply to said tanks, means for selectively
opening and closing said upper and lower openings, said upper
openings being normally open and said lower openings being normally
closed, means for individually pressurizing each tank to a pressure
above the pipeline pressure when said associated upper opening is
closed to cause the product to flow from the tank into the venturi
assembly through said lower opening, means for sensing a
predetermined fill level of product in each tank, means for
detecting said upper and lower openings are closed, and control
means for automatically regulating feed of the product to the
venturi assembly and into the pipeline in response to said sensing
and detecting means so as to maintain a steady and controlled flow
of product through the venturi assembly and pipeline without
degrading the air flow in the venturi by verifying proper and
alternate product flow into and out of said tanks wherein one tank
is discharging product into the venturi assembly as the other tank
is filling with product, said control means verifying prior
discharge of product from said other tank to be filled by
monitoring said sensing means to determine the absence of product
in said other tank, if discharge is not verified, said control
means deactivating said suppy means and activating said
pressurizing means to temporarily pressurize said other tank and
discharge product therefrom in a recycle mode; if discharge is
verified, said control means then activating said pressurizing
means to pressurize said one tank to be discharged when said
sensing means indicates said one tank is filled and said detecting
means indicates said associated lower opening is closed.
18. An apparatus as set forth in claim 17, wherein for initial fill
of said tanks said control means opens said supply valve means when
said detecting means indicates said lower openings are closed and
said upper openings are open and said control means inhibits said
pressurizing means, said control means closing said supply valve
means under any other conditions.
19. An apparatus as set forth in claim 17, wherein activation of
said pressurizing means closes said associated upper opening and
opens said associated lower opening at a predetermined pressure in
said tank.
20. An apparatus as set forth in claim 19, wherein said control
means includes timer means for controlling pressurization time of
said one tank, said pressurization time being less than an overfill
time of said other tank.
21. An apparatus as set forth in claim 20, wherein said control
means includes latch means for providing a continuous indication
that said one tank is full during said pressurizing time, said
latch means being reset at the end of said pressurizing time.
22. An apparatus as set forth in claim 20, wherein after said timer
means times out, said control means deactivates said one tank
pressurizing means and activates the other tank pressurizing means
when said other tank detecting means indicates said associated
lower opening is closed and said sensing means indicates said other
tank is filled.
23. An apparatus as set forth in claim 19, wherein said control
means closes said supply valve means when said sensing means
indicates said one tank did not properly discharge during said
pressurization time.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates generally to pneumatic apparatus for
conveying particulate material. More specifically, the invention
relates to an apparatus for feeding material to a pipeline from a
supply and a control system for maintaining continuous duty
operation.
2. Discussion of the Related Art
A pneumatic conveying apparatus for transporting pulverulent,
powdery, granular, liquid or like material and products is
described in U.S. Pat. No. 4,111,492, issued to Mraz, and such
disclosure is fully incorporated herein by reference. The apparatus
generally includes a pair of tanks each having a product receiving
conduit at the upper end thereof. Door-like valve members are
provided to open and close respective upper and lower openings for
feeding product into and out of the tanks. A Y-shaped housing
provides a dual channel arrangement for separately feeding the
product from each tank into the pipeline via a venturi assembly.
The product is fed to the pipeline by alternately pressurizing the
tanks, one tank filling while the other tank empties.
While the pneumatic conveying apparatus shown in the referenced
letters patent is a substantial advance in the art, there are
limitations because a technician operating the apparatus must
closely watch and inspect the machine to verify safe and proper
operation. In particular, it is important to ascertain that the
tanks are properly emptying and filling, that the venturi assembly
receives a continuous, steady, and controlled flow of material
without disturbing or degrading the air flow in the venturi, and
that there is not a blockage in the system, especially of one or
more of the numerous valves. Also, the door-like valve members have
been found to exhibit fatigue over extended operating periods,
resulting in degraded seal integrity.
SUMMARY OF THE INVENTION
Accordingly, the present invention comtemplates a new and useful
pneumatic conveying apparatus for feeding material through a
venturi assembly to a pipeline which has means for automatically
controlling continuous duty operation of the apparatus with minimal
operator interface. One aspect of the invention is a programmable
controller which monitors a plurality of sensing and detecting
devices which provide inputs to the controller indicative of the
operating status of the conveyor. The controller activates and
deactivates a plurality of product feed mechanisms in response to
the monitored inputs to sustain a substantially continuous flow of
product through the venturi while maintaining proper overall
operation of the conveyor.
According to another aspect of the invention, a controller is shown
for a pneumatic conveying apparatus wherein the controller ensures
that the only direction of release of the product is into the
venturi assembly and the pipeline.
A further aspect of the invention is a flapper door valve for
closing the product inlet and outlet openings of the tanks. The new
valve is less susceptible to pivot fatigue and maintains its seal
integrity over an extended period of time. The door valve is also
designed to permit movement or removal of the door through the
associated conduit which is closed by the valve.
These and other aspects of the invention will be more fully
described and understood in the following specification in view of
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevation in partial section of a pneumatic
conveying apparatus according to the present invention;
FIG. 2 is a rear elevation of the apparatus of FIG. 1;
FIG. 3 is a flow chart diagram of a system steady-state operation
for the controller used with the apparatus of FIG. 1;
FIG. 4 is a flow chart diagram of a system start-up cycle for a
controller used with the apparatus of FIG. 1;
FIG. 5 is an elevation in section of a flapper door used with the
apparatus in FIG. 1; and
FIG. 6 is a perspective view of the door of FIG. 5 shown mounted on
a conduit and in an open position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A pneumatic extrusion and conveying apparatus for feeding
particulate produce to a pipeline is generally indicated by the
numeral 10 in FIGS. 1 and 2. Such apparatus 10 has two
longitudinal, upright tanks 12a and 12b adapted to hold separate
quantities of a product 14. Each tank is generally cylindrical in
section, but includes an inverted and truncated conical section 16
at a lower end thereof.
At the upper end of each tank is a product receiving conduit 18a
and 18b respectively, for entry of the product into the interior
chamber of the tank. The product 14 is supplied from a supply
hopper 20, as illustrated. A conventional electrically controlled
butterfly valve 22 is provided to control the feed of product from
the hopper 20 to the tanks 12a, 12b.
The inner ends of the product conduits 18a, 18b define upper
openings 24a and 24b, respectively, for feeding the product 14 into
the tanks. As illustrated, the conduits 18a, 18b extend into the
tanks with their longitudinal axes extending downwardly at about
60-degree angle from horizontal. This conduit orientation promotes
quick filling of the tanks 12a, 12b without material hang-up,
because the angle of repose for many materials is less than 60
degrees. Of course, other entry angles for the conduits may be
selected, depending on the particular flow characteristics of the
product 14 being conveyed.
At the conduit inner ends are upper flapper door members 26a and
26b, respectively. These doors 26 are of similar construction and
act as means for opening and closing the product feed openings 24a,
24b. As illustrated, one flapper door 24a is shown in the closed
position and the other door 24b is shown in the normally open
position. The construction and mounting of the doors 26 will be
described in greater detail hereinbelow. For now, it will suffice
to state that each flapper door 26a, 26b is mounted in a hinge-type
arrangement 28 so that the doors open and close the conduits 18a,
18b by a simple pivotal movement about the hinge axis. The flapper
doors hang generally vertically under their own weight in the
normally open position, and each door is independently actuable to
close its respective feed opening, so that during steady-state
operation, one tank can be filled while the other or opposite tank
is being emptied.
The lower conical section 16 of each tank provides an outlet 30
communicating with a Y-shaped housing 32 which is flanged at its
two upper ends for attachment to mating flanges surrounding the
outlets 30. The housing 32 has two product channels 34a and 34b,
one for receiving product from each of the tanks 12a, 12b,
respectively. The product channels 34a, 34b extend down from the
conical sections 16 and then generally horizontally towards each
other and open into a common closed chamber 36 which is part of the
housing 32. The chamber 36 opens at the lower end thereof into a
venturi assembly 37, the operation of which will be more fully
described hereinafter. The venturi assembly 37 is shown somewhat
schematically in FIG. 1. Complete disclosure as to the construction
and operation of the venturi assembly is provided in U.S. Pat. No.
4,009,912, the entire disclosure of which is incorporated herein by
reference. The channels 34a, 34b respectively define lower openings
38a and 38b for feeding the product 14 from the tanks to a pipeline
40 via the Y-shaped housing 32 and the venturi assembly 37. By
using 90-degree elbows for the product channels 34a, 34b, the lower
openings 38a, 38b are displaced laterally of the corresponding
outlet 30 at the lower end of each tank 12a, 12b. This helps reduce
the force tending to open lower flapper doors 50a, 50b due to the
weight of the product.
The closed chamber 36 is provided by walls 42 and surrounds the
lower feed openings 38a, 38b. The chamber 36, during operation, is
at less than atmospheric pressure because it is in communication
with a feed chute elbow 44 within the venturi assembly 37. The
elbow 44 extends into a portion 40a of the pipeline 40 through
which a carrier gas comprising a high velocity stream of air is
forced by an air compressor 46. The high air velocity about the
transition area 48 of the feed chute elbow 44 creates a reduced
pressure in the chamber 36.
Each of the lower openings 38a, 38b is provided with a valve member
in the nature of a lower flapper door 50a, 50b, respectively, which
can be of similar construction to the upper flapper doors 26a, 26b.
Preferably, the lower openings 38a, 38b lie in generally vertical
planes such that the lower flapper doors 50a, 50b hang in a
normally closed position as compared with the upper flapper doors
26a, 26b, which hang in a normally open position. Each lower
flapper door is mounted in a hinge-type arrangement so that each
door opens and closes its associated lower opening by a simple
pivotal movement about the hinge axis.
As illustrated in FIG. 1, one lower flapper door 50a is shown in
the open position and the other lower flapper door 50b is shown in
the closed position. The facing ends of the channels 34a, 34b are
spaced apart so that when one of the lower flapper doors (in the
illustrated case, door 50a) is open, it interferes with and
substantially prevents the other door from opening.
The air compressor 46 shown in FIGS. 1 and 2 may be a conventional
turbine-type machine, and is used to supply compressed air or other
suitable primary carrier gas through the pipeline 40 and to the
tanks 12a, 12b. Compressed air is supplied to the pipeline 40 via a
conduit 52.
Referring to FIG. 2, the compressor 46 also supplies compressed air
through a conduit 54 to a tee coupling 56 and conventional
electrically actuable solenoid valves 58a and 58b to pressurizing
pipes 60a and 60b, which extend into the tanks 12a, 12b,
respectively. As will be more fully described hereinbelow, the
valves 58a, 58b are controlled so that only one of the pipes 60a,
60b is supplied with compressed air at any given time and only when
the corresponding lower flapper door 50a, 50b is closed.
Referring again to FIG. 1, the pressurized pipes 60a, 60b enter
their respective tanks transversely through a wall 62 thereof. The
pipes 60a, 60b open into the interior of the tanks 12a, 12b
generally facing an outer surface 64 of the associated upper
flapper door 26a, 26b. Thus, when one of the valves 58a, 58b is
open, high velocity air is directed at and acts on the
corresponding upper flapper door 26a, 26b and the force of the
compressed air stream sealingly closes the respective upper feed
opening 24a, 24b by swinging the actuated door 26a, 26b up against
the inner end of the corresponding product receiving conduit 18a,
18b (as illustrated in FIG. 1 with door 26a).
Air relief or vent valves 66a and 66b, shown in FIG. 1 only, are
provided in the upper portions of the tanks for purposes which will
be more fully apparent hereinafter. The air relief valves are
conventional in design and are electrically actuable. A plurality
of inspection windows 68 (only one shown in FIG. 1) are provided to
permit visual observation of the operation of the apparatus 10, if
desired.
The mechanical and functional steady-state operation of the
apparatus 10 will now be described. Before the air compressor 46 is
turned on, the lower flapper doors 50a, 50b are both in the
normally closed position even when the tanks 12a, 12b are filled
with product 14. The upper flapper doors 26a, 26b are normally open
and, assuming, as is customary, a supply of product is in the
hopper 20, both tanks 12a, 12b will be filled when the butterfly
valve 22 is opened. The valves 58a, 58b (FIG. 2) are both initially
closed, which permits the air compressor 46 to be started and to
reach a stable operating point and assure proper pressure in the
pipeline 40.
When one of the tanks 12a, 12b is filled, its corresponding vent
valve 66a, 66b and solenoid valve 58a, 58b are opened. For
illustrative purposes only, it will be assumed that tank 12a is
first filled and initiates the discharge cycle operation; however,
as will be apparent, either tank 12a or 12b may be the first to be
filled and initiate operation.
As stated, with the tank 12a filled, the valve 58a is opened and
supplies a blast of air against the adjacent face of the open upper
flapper door 26a. The pressure of the air is effective to force the
door 26a to swing and close off the upper product feed opening 24a
of the conduit 18a. The pressure of the air on the upper surface of
the product quickly increases to a level where the product 14 and a
predeterminable amount of carrier gas discharges from the tank 12a
into the Y-shaped housing 32.
The product 14 is biased by the air into the Y-shaped housing 32
via the 90-degree elbow product channel 34a. The static head, due
to the weight of the product and the increasing air pressure,
causes the lower flapper door 50a to swing open so that the product
14 flows into the chamber 36. The door 50a also maintains the other
door 50b closed notwithstanding the subatmospheric pressure in the
chamber 36 and the weight of the product 14 against the closed door
50b.
The product 14 and a predetermined amount of carrier gas at a
specified pressure enter the venturi assembly 37 through a lower
opening in the chamber 36. As the material and gas travel through
the venturi core, the product is concentrated at the centerline of
the pipeline as illustrated. As the product 14 and carrier gas exit
the venturi core, they meet primary carrier gas traveling in the
venturi 37 via a portion 40a of the pipeline. This predetermined
amount of carrier gas at same pressure causes the product 14 and
carrier gas to remain compressed in the centerline of the pipeline
40. Since the product 14 is already at some average "speed," the
transfer into the pipeline 40 is smooth and efficient. The
combination of the pressure pushing on the product 14 in the tank
12a, the subatmospheric pressure in the chamber 36 and elbow 44,
and the high air velocity at the transition area 48 causes a rapid
acceleration of the material as it flows from the housing 32
through the venturi 37 and into the pipeline 40. The distance down
the pipeline that the product remains in the described condition
depends upon the product material characteristics, the amount of
carrier gas entrained in the product, the pressure and volume of
the primary carrier gas, and the ratio of the cross-sectional area
between the elbow 44 and the pipeline portion 40a. This ratio or
setting depends upon all described conditions, but also creates the
subatmospheric pressure in the elbow 44 and the chamber 36 which
increase the efficiency of the "force" moving the product 14 from
the tanks 12 to the pipeline. This effect is common to all
inductors, but is unique when the product is conveyed in a
push-pull condition as described and enters this low pressure
region located in the centerline of the pipe. This condition may
result in the Reynolds number normally associated with gas flows in
a pipeline at the condition to be modified. At what point the
traditional Reynolds number of gas/solids flow are effected depends
upon terminal velocity of the product and the specific gas
conditions at the time. The flow of air through the pipeline 40 can
be adjusted with a valve (not shown) to enhance the feed of product
into the pipeline.
While the tank 12a is being pressurized, the other tank 12b is at
ambient pressure and product 14 continues to flow into the tank 12b
to fill it. The associated vent valve 66b is open to exhaust air
from the tank which is displaced as product fills the tank.
After a predetermined discharge time, the solenoid valve 58a is
closed and the tank 12a is returned to ambient pressure by opening
the vent valve 66a, thereby discharging a predetermined amount of
carrier gas, and the discharge cycle is complete. The carrier gas
can be cleansed of any product during venting of the tank by the
use of a filter (not shown). When the tank 12a is vented to a
sufficient degree, the flapper door 26a swings back to its original
open position and the flapper door 50a is lacking the force of the
bulk solids and carrier gas to remain open and returns to its
original closed position. With the door 26a open, the product 14
feeds into the tank 12a through the opening 24a and refills the
discharged tank.
When the air flow through the pressurized pipe 60a is turned off
and the product starts to enter the tank 12a, the lower flapper
door 50a closes sufficiently soon that the other lower door 50b can
open.
When the first tank 12a is returned to ambient pressure, the
opposite tank 12b is immediately pressurized and the process
repeats in a similar manner. The tanks 12a, 12b alternately fill
and empty in a complementary manner as long as product 14 is
available from the support hopper 20.
The present invention contemplates the use of a programmable
controller 70 in combination with the above-described apparatus 10
and various sensors and detectors which provide operational status
indicators to the controller 70. The controller regulates and
maintains the pneumatic apparatus 10 in a continuous duty mode of
operation so as to enhance and maximize the advantageous operation
and use of the venturi assembly 37. The controller 70 has a
plurality of inputs 72 which receive the signals from the sensors
and detectors and a plurality of outputs 74 which are connected to
the various valves described hereinabove.
According to the invention, there is provided a proximity sensor or
detector switch 76 associated with each of the upper flapper doors
26a, 26b and each of the lower flapper doors 50a, 50b. The switches
76 can be of conventional design of the type which detect the
nearness of a metal object in a continuous magnetic field of a
specific dimension. The switches 76 are arranged as illustrated
such that they are actuated when the doors 26a, 26b, 50a, 50b are
closed. A plurality of conductor wires 78 connect the outputs of
the switches 76 to the appropriate inputs 72 of the controller
70.
There is also provided in each tank 12a, 12b a fill level sensor or
probe 80a and 80b, respectively, each probe being generally
positioned as illustrated in FIG. 1. The spatial location of each
probe 80 is a nominal fill location and depends upon the type of
bulk material being conveyed, the type of pipeline 40 and its size,
the air pressure and volume to be used, and the distance the
product is conveyed. The sensors 80 are of conventional design,
which operate at a constant integrated frequency until a solid-like
material touches the sensor. The operating frequency is then
changed to a second frequency until the solid is removed. A set of
conductor wires 82 connect the outputs of the sensor 80 to the
appropriate inputs of the controller.
As illustrated in FIG. 1, high and low-pressure switches 84 and 86
are positioned in the pipeline 40 downstream of the housing 32. The
pressure switches are conventional, and provide output signals to
the controller 70 which indicate when the pipeline pressure exceeds
or falls below predetermined levels for proper operation of the
apparatus 10. A set of thumbwheel switches 87 provide a convenient
means for the operator to dial into the controller 70 the
appropriate pressure limits for operation of the apparatus 10.
Conductor wires 88 connect the outputs of the pressure switches 84,
86 to appropriate inputs on the controller 70. The controller 70
continuously monitors the pressure switches, and when the pressure
in the pipeline is not within the predetermined high and low
limits, the controller shuts down the apparatus 10.
A pair of conductor wires 90 (FIG. 2) connect an appropriate drive
output of the controller 70 to the butterfly valve and a set of
conductor wires 92 connect the appropriate drive outputs of the
controller 70 to the air solenoids 58a, 58b. Another set of
conductors 94 (FIG. 1 only) connect the appropriate outputs of the
controller 70 to the vent valves 66a, 66b. A master on/off switch
96 is provided with the controller 70 for operator control of the
apparatus 10. The switch 96, of course, may also be located remote
from the controller 70.
A suitable controller 70 for use with the invention is the Omron
Model Sysmac S6, manufactured by Omron Electronics, Inc., Chicago,
Ill. The high pressure switch 84 can be Transamerica Deleval Model
EIH-H90, manufactured by Transamerica Deleval, Los Angeles, Calif.,
and the low pressure switch 86 can be Transamerica Deleval Model
EIH-H-15, manufactured by Transamerica Deleval, Los Angeles, Calif.
A suitable proximity switch 76 is Model 8035A105 FL3NAXX,
manufactured by Automatic Timing and Controls Company, King of
Prussia, Pa. The level probes 80 are preferably Model 602R IF,
manufactured by Monitor Manufacturing Company, Elburn, Ill.
The purpose of the above-described instrumentation and controller
is to provide continuous duty operation, meaning that the apparatus
10 will operate at a predetermined capacity for a given percent of
availability for a predetermined duration. The controller 70
monitors the internal operation of the apparatus 10 to assure that
each cycle is completed prior to initiating the next cycle. By
maintaining a continuous duty operation, the controller 70
substantially enhances the accelerated extrusion of the product 14
into the pipeline 40, as described hereinbefore, via the venturi
assembly 37. The controller maintains a continuous uniform flow of
product into the vortex of the venturi without creating turbulence,
and thus not degrading the uniform flow of the high velocity
venturi air flow. The usefulness of the venturi assembly 37 is
therefore enhanced since, otherwise, the venturi assembly is not a
self-regulating mechanism. The functional operation of the
controller 70 and related instrumentation will now be described, it
being realized that such description is exemplary only for
illustrating the concepts of the invention.
Turning now to FIG. 4, a flow chart is shown for the initial
start-up sequence for the apparatus 10, wherein it is assumed that
the tanks 12a, 12b are empty but there is a supply of product 14 in
the hopper 20.
The master on/off switch 96 initiates a reset step in the
controller 70 and turns on the air compressor 46. The controller 70
verifies that the pipeline 40 pressure is within the high and low
limits (P.sub.1 and P.sub.2, respectively) dialed in by the
operator using the thumbwheel switches 87. The controller 70 reads
the proximity switches 76 adjacent the upper flapper doors 26a, 26b
and if either one is activated, which indicates the corresponding
door is closed and not in its normally open position, the start-up
sequence is terminated and an LED warning light 98 is lit on the
controller 70 to indicate to the operator why the machine is not
running. The controller 70 also checks that power is being applied
to the solenoid valves 58a, 58b to hold the valves closed so that
neither tank 12a, 12b is pressurized during start-up. The
controller further checks that both lower flapper doors 50a, 50b
are closed, as indicated by activation of the associated proximity
switches 76. If the doors are not closed, another LED light 100 is
illuminated and system start is aborted.
The controller 70 then waits ten seconds, following which it opens
the butterfly valve 22 and the product 14 flows into the tanks 12a,
12b. This completes the start-up phase of operation.
Turning now to FIG. 3, there is shown a flow chart for steady-state
operation of the apparatus 10. Herein, it is presumed that the
start-up sequence has either just been completed or that at least
one of the tanks 12a, 12b is filled from a previous run operation.
For purposes of describing the steady-state operation, it will be
presumed that the left tank 12a fills first or initiates operation,
it being realized that either tank 12a, 12b can initiate operation.
The flow chart shown in FIG. 3 only gives detail as to the left
side or first tank operating sequence. The right side or second
tank operating sequence is substantially identical in function,
although, of course, duplicate circuits are provided as
required.
After start-up, the controller 70 monitors the level probes 80a and
80b, respectively located in the tanks 12a, 12b as illustrated in
FIG. 1. When one of the probes 80a, 80b indicates that a
predetermined fill level of product 14 is in the associated tank,
the pressurizing and discharge operation commences. The left level
probe 80a (which is presumed to trip first) triggers a conventional
resettable latch 102 in the controller 70. The latch 102 is used
because as soon as the level probe 80a detects a filled condition,
the controller immediately pressurizes the tank 12a, and product 14
begins flowing out of the tank into the housing 32. The level probe
80a can thus become uncovered too soon, which would prevent the
discharge cycle from being completed. The latch 102 is used to
essentially "fool" the control section into operating as if the
probe 80a were still covered with product until the discharge cycle
is completed.
When the level probe 80a indicates the fill level is reached, the
controller 70 verifies that the corresponding lower flapper door
50a is closed by checking if the associated proximity sensor switch
76 is activated. If not activated, the controller 70 illuminates
the LED warning light 100 and shuts down the apparatus 10.
Normally, however, the lower door 50a is closed and the controller
70 closes the vent valve 66a and opens the solenoid-actuated
pressurizing valve 58a. Up to this time (at which activation of the
level probe 80a occurs), the vent valve 66a has been open to permit
air displaced by the feeding product 14 to escape the tank 12a.
Opening the valve 58a directs pressurized air from the compressor
46 to the pipe 60a. The pressurized air entering the tank 12a via
the pipe 60a forces the upper flapper door 26a to swing into a
closed position as illustrated in FIG. 1. With the door 26a closed,
the tank 12a is pressurized to apply an increasing downward force
on the product 14. The pressure builds up so as to discharge the
product out through the lower flapper door 50a, which is forced
open, and then on into the pipeline 40 via the venturi assembly 37,
as previously described herein. The open lower door 50a interferes
with and maintains the opposite door 50b closed during the
pressurization of the tank 12a.
The air flow through the solenoid valve 58a continues for a
predetermined period of time, which is determined by a timer 104 in
the controller 70. The length of time that the tank 12a is
pressurized depends, of course, on the specific application, but
typically is between two and seven seconds.
While the product 14 in tank 12a is being discharged or fed out of
the tank, the opposite tank 12b continues to fill with the product
14 even after its associated level probe 80b is covered. The
discharge time of tank 12a is less than the amount of time it would
take to overfill the opposite tank 12b to a degree which would
interfere with the intended operation of the apparatus.
When the timer 104 times out, the latch 102 is reset and the
controller 70 closes the valve 58a and checks if the level probe
80a is deactivated, indicating that product discharge is completed.
If the level probe 80a indicates that product 14 is still in the
tank 12a, it usually means that the upper flapper door 26a is stuck
open, so a recycle mode 106 is initiated. When the tank 12a fails
to empty during a discharge period (i.e., the level probe 80a is
actuated), the butterfly valve 22 is closed by the controller and
the air pressure valve 58a is reopened. This is done to try to
develop enough pressure build-up against the butterfly valve 22 to
take the place of the stuck-open flapper door valve 26a. A counter
108 is used to control the number of recycle attempts made prior to
shutdown. Typically, two attempts will be made.
Usually, however, after the timer 104 times out, the level probe
80a indicates that the discharge cycle is complete, so that the
recycle mode is not performed. The controller 70 then opens the
exhaust or vent valve 66a. The controller also reopens the
butterfly valve 22 if it was closed due to a recycle operation.
When the valve 66a is opened, the tank 12a returns to ambient
pressure. The upper flapper door 26a is again in its normally open
position and the lower door 50a is in its normally closed position,
and the product 14 begins to feed into the discharged tank 12a and
refill it.
As shown in FIG. 3, when the discharge cycle in the first tank 12a
is completed, the controller checks that the opposite tank 12b is
filled and then initiates a discharge cycle in tank 12b as tank 12a
refills. The discharge cycle of the opposite tank is functionally
the same as the first tank, and therefore is not illustrated in
FIG. 3 and need not be described in detail. The tanks 12a, 12b
alternate fill and discharge cycles in a continuous duty mode so
long as there is product in the hopper 20, the lower flapper door
50 on the respective discharge tank is closed prior to
pressurization, and the pipeline 40 pressure is within the preset
limits.
It will be apparent from FIG. 3 that a tank which has completed a
discharge cycle will begin to refill with product 14 even if the
associated lower flapper 50 does not fully close (i.e., the
proximity switch is not activated). This is done in the hope that
the opening of the opposite door 50 during pressurization of the
opposite tank will close the stuck door. After the opposite tank
has discharged, if the lower door of the first tank is still open,
the controller 70 then shuts down the apparatus 10. Thus, a
discharge cycle cannot occur if the lower flapper door is open
prior to pressurization, but one refill cycle per tank can occur
with a lower door stuck open.
It should also be apparent from FIG. 3 that the vent valves 66a and
66b always operate in a complementary manner during steady-state
operation, i.e., when one is open (during a fill cycle), the other
is closed (during a discharge cycle). This interlock is programmed
into the controller 70 to assure that as one of the tanks 12a, 12b
is being pressurized, the other tank is not, so that the only
direction of release of product 14 is through the housing 32 into
the pipeline 40.
Although only shown in FIG. 4 for clarity, during the start-up
cycle or the steady-state cycle of either tank 12a, 12b, if the
pipeline 40 pressure falls outside the predetermined envelope
monitored by the high and low pressure switches 84, 86, the
controller 70 closes the butterfly valve 22 and shuts down the
system. The controller is programmed to try to restart the system
five times, using a counter 110 and comparator 112, in two-second
intervals. Of course, the number of attempts and the duration of
the attempts can be modified with simple software variations.
While the preferred embodiment has been described as operating with
a predetermined discharge time controllable via the timer 104, it
is also contemplated that the controller 70 can control operation
based on the actual level of product 14 in the discharging
tank.
Furthermore, the fill level probes 80a, 80b may be unsuitable for
certain product materials such as cement. When the apparatus 10 is
to be used with such materials, the controller 70 provides an
internal timing function in place of the level probes (not shown)
to meter the fill time of the tanks 12a, 12b and begins the
discharge cycles after the timer has elapsed. In this situation,
the timer essentially acts as a means for sensing a predetermined
fill level of the product in the respective tank. The functional
operation of the apparatus 10 and controller 70 is otherwise the
same as described herein.
The invention also contemplates an improved flapper door and
mounting arrangement therefor which will now be described. Such a
door can be used for both the upper and lower door 26, 50, although
the mounting arrangements can be different.
Turning to FIGS. 5 and 6, a flapper door is generally indicated by
the numeral 120. The door comprises two facing layers 122 of a
resilient material such as rubber with a layer 124 of woven glass
fiber 123 sandwiched between the layers 122. The glass fiber layer
124 is preferably bonded directly to the adjacent rubber surfaces,
with a suitable bonding material known in the art.
A metal plate 126 is mounted with cement to the inner side 128 of
the rubber layer which faces a conduit or chute 130 which the door
120 is used to sealingly close. The metal plate 126 is formed of
sheet steel or other suitable material, and it is sized so as not
to contact the perimeter of the chute 130 so that only the rubber
layer 124 presses against the chute and forms a seal.
The outer side 132 of the opposite rubber layer 122 has mounted
thereon a second metal plate 134. A through-bolt and nut assembly
136 holds the door assembly, and in particular the plates 126, 134,
together.
As best shown in FIG. 5, the flapper door 120 includes a hinge-like
extension member 138 adapted to be fixedly mounted to the conduit
130 or other suitable structure with a hanger 150. The member 138
is a lateral coextension of the rubber and glass fiber layers, and
is shown spaced from the hanger 150 in FIG. 5. Thus, the door 120
is free to swing between an open position and a closed position
with respect to the conduit 130. The door 120 is further provided
with a horseshoe-shaped cup member 140 which is mounted as
illustrated on the outer plate 134.
The durometer of the rubber layers 122 is preferably selected to
minimize the force required to move the flapper door 120 while
maintaining the hinge point integrity to prevent early fatigue.
The outer plate 134 carries the load of closing the flapper door
120 against the open end of the conduit 130 by providing a surface
against which a force can be applied to swing the door 120 closed
without damaging the rubber layers 122. The inner plate 126
provides a wear surface to protect the rubber layer which faces the
conduit 130. When the force to swing the door 120 is applied via a
high pressure air stream from a conduit 60 (as in FIG. 1), the
horseshoe member 140 catches the air as the door 120 pivots so that
the air continues to push on the door 120. The glass fiber layer
124 provides a substantial structural reinforcement to the door 120
and limits deformation of the rubber layers 122. Other fiber-woven
materials may be used when appropriate.
Because the rubber layers 122 are cemented to the galss fiber 124
and the plates 126, 134, the rubber must accommodate elongation of
the glass fiber layer which occurs as the door pivots about the
hinge axis. The rubber must also have sufficient compression to
prevent relative movement between the rubber layer 122 and the
plates 126, 134.
The peripheral edge 142 of the conduit 130 is preferably formed
with a rounded surface to improve the seal integrity when the door
is pressed against the conduit. The radius of the edge 142 is
selected to maximize seal pressure for a given operating or system
pressure used to swing the flapper door 120 closed. Typically, the
radius is one-half the conduit wall thickness.
As best shown in FIG. 6, although the conduit 130 is typically a
round pipe, the door 120 has two opposed, longitudinal, straight
sides 144 which join two opposed ends 146. The straight
longitudinal sides 144 are spaced so as to provide a width to the
door 120 which is less than the diameter of the conduit 130,
thereby making it possible to remove the door through the conduit.
This simplifies access to and removal for repair or replacement of
the door. To assure a complete seal of the conduit 130, the open
end thereof is provided with two opposed metal chord-like sections
148 (only one shown) which compensate for the reduced width of the
door 120. Thus, the door 120 actually closes off the conduit 130 by
sealing against a part of the circumferential periphery of the
conduit and the edges of the chord sections 148. For clarity, the
rubber and fiber layers are only shown schematically in FIG. 6.
Turning again to FIG. 1, a door such as just described is shown
somewhat schematically, and is used as the upper flapper doors 26a,
26b for the apparatus 10. As illustrated, a hinge mounting means 28
(which can be similar to hanger 150 in FIG. 5) is provided on which
the door is mounted. In the prior art (not shown), this hanger 28
was placed at 90 degrees with respect to the conduit 18 so that
when the door was open a substantial stress was applied to the door
and resulted in early fatigue, typified by separation or
delamination of the rubber layer and glass fiber layer. According
to the present invention, as illustrated in FIG. 1 and also in FIG.
5, the hanger angle 152 is increased by about 20 degress, from 90
degrees to 110 degrees, to reduce the stress on the flapper when it
hangs in its normally open position.
The change in the hanger angle 152 results in part from the fact
that the feed conduits 18a, 18b open into the tanks 12a, 12b at an
angle other than vertical. Thus, the doors 26a, 26b are stressed in
the normally open position. In the case of the lower flapper doors
50a, 50b, however, since each discharge elbow 44 opens in a
vertical plane, the doors 50a, 50b hang normally closed in a
vertical unstressed condition. Thus, a mounting hanger 154 for the
lower doors can be fixed at 90 degrees with respect to the
longitudinal axis of the elbow 44.
It will be appreciated that the important consideration is to
reduce the stress on doors 26, 50 in their normal position, be it
open or closed, since the doors are out of such position only
during pressurization of the tanks 12a, 12b.
It should be evident that this disclosure is by way of example and
that various changes may be made by adding, modifying or
eliminating details without departing from the fair scope of the
teaching contained in this disclosure. The invention is therefore
not limited to particular details of this disclosure except to the
extent that the following claims are necessarily so limited.
* * * * *